Patent GB-191515377-A (GB)
Title: Improvements in Machines for Grinding Glass.
Inventor: TAYLOR WILLIAM
IPC: B24B27/00
Filed: 1915-11-01
Abstract: 15,377. Taylor, W. Nov. 1. Disk and wheel apparatus; lenses and curved surfaces of mirrors, grinding and polishing; bevelling.-Relates to a machine for grinding spherical surfaces and bevels on lenses, mirrors, or other glass disks, of the kind in which the disks are carried by rotatable spindles and abrasive wheels are employed, and comprises means for setting the axes of an abrasive wheel and a work spindle in variable operative relation in or out of a common plane, and means whereby a relative feed between the abrasive wheel and the work spindle is automatically effected. In the semi-automatic machine shown, the work spindles are mounted in a turret 1 which is moved towards the abrasive wheels 4, 5 to feed the work and is rotated to carry the work into positions for roughing and finishing and for permitting a finished lens &c. to be replaced by a fresh blank. The turret 1 is secured to a shaft 1<b> journaled in a slide 2 which runs on V-ways 7<e>, 7<d>. Three hollow spindles 3, 3<a>, 3<b> are mounted in the turret, each being provided with an ordinary split chuck 3<h> for a blank 24. In the position shown in Figs. 1 and 2, the blanks on the spindles 3b, 3 are in position to engage the roughing-wheel 4 and the cup-shaped finishingÀwheel 5 respectively, and the finished lens on the spindle 3<a> is in position for removal. The wheel 5 is secured to a shaft 5<a> journaled in the top slide 5<f>, Fig. 1, of a slide-rest, the bottom slide being mounted on a table 5<i> which is rotatable on a seating about a vertical axis 5<k> and is provided with a setting-scale 5<x>. The axis 5<k> intersects the axis of the work spindle 3 at the edge of the wheel, and the axis of the spindle and the wheel are in the same plane. By rotating the table 5<i>, the axis of the wheel can be inclined to the axis of the spindle at the angle to be determined by the radius of the spherical surface being ground. Further, by means of screws 1<m>, 1<n> described below, the turret can be set so that the axis of the spindle 3 is slightly above or below the axis of the wheel, according to whether a convex or a concave surface is being ground. The wheel 5 is traversed by means of the screws 5<g>, 5<h> of the slide-rest. The roughing-wheel 4 is mounted with its axis at right-angles to the work spindles and preferably with one face in the plane of the adjacent spindle 3<b>. The wheel 4 can be fed and also adjusted to bring its axis into or out of the same plane as the axis of the spindle 3b, for grinding a cavity or for bevelling respectively, by the following device. The carrier 4<f>, Fig. 2, for the wheel is secured to a bracket 4<g> by a bolt 4<i> passing through a vertical slot 4<l> in the bracket, and by a bolt 4<h> passing through a vertical slot 4<j> in the carrier and an horizontal slot 4<k> in the bracket. The carrier is adjusted vertically by means of a screw 4<m> and is adjusted pivotally about the bolt 4i by means of a stay which engages a stud 4<g> on the carrier and is threaded to engage a screw 4s, which is journaled in a pivoted block 4<u> and is operated by a hand-wheel 4<t>. The spindles 3, 3<a>, 3b each receive a rod to which is secured a pulley 3<j>, 3<j1>, 3<j2> and a chuck, a spring arranged between each spindle and pulley drawing the chucks inward. To render uniform the thicknesses of the finished lenses, the three chuck-rods with the chucks are made of uniform lengths, and the rods are pressed by the grinding-wheels against abutments 2<i>, 2<j> on a bracket 2<h> on the slide 2. The chuck spindles have limited longitudinal freedom in the turret. The finished lens is released by means of a plunger 2<k>, Fig. 2, which can be thrust against the idle chuck-rod by operating a crank 2<p>. The chucks are rotated by means of a band 13<f> which passes round a pulley 13<d> on the bracket 2<h> and round the pulleys 3<j1>, 3<j2> of the active chucks, the pulley 3<j> of the idle chuck being, as shown in Fig. 5, out of contact with the band. The pulley 13<d> is driven by a belt 13<a> from a shaft 6<n> geared to a shaft 6<k> carrying a driving-pulley 6<j>. The turret is reciprocated by means of a shaft 6<a> provided with a crank-pin 6e carrying a block 6<f> which engages a slot 6<g> in the slide 2. During the rotation of the crank from the position shown in Fig. 2, the turret is advanced and then withdrawn, the blanks thus being brought up to the grinding-wheels, ground, and then withdrawn. The grinding is effected while the turret is being advanced slowly owing to the crank approaching the dead-centre. To permit of a quick advance and withdrawal of the turret, an auxiliary slow-speed drive, described below, is provided for driving the shaft 6<a> while grinding is being effected. The shaft 6<a> is normally driven by a worm 60 on the shaft 6<n> which engages a loose worm-wheel 6<p> which is pressed against a flange 6<r> by a plate 6<t> urged by a spring 6
. The plate 6<t> is feathered on the shaft and may be provided with a friction surface 6<u>. Towards the end of the advance of turret, the shaft 6<a> is driven at a slower speed by means of a worm 8<b> on a shaft 8<c>, which is driven at variable speeds by means of a band 8<d> passing over stepped pulleys on the shafts 6<n>, 8<c>. The worm 8<b> engages a loose worm-wheel 8<a> formed with a hub 8<i>, Fig. 5, arranged in a collar 8<j> secured to the shaft. A friction pawl pivoted on the collar is pressed by a spring towards the hub 8<i>, but is normally held inactive by the engagement of the tail of the pawl with a fixed circular flange 8<q>. The flange is cut away for about one-third of the circumference, and the length of the gap can be adjusted by means of a sliding shutter 8<u> which is secured by a nut 8<w>. In operation, the turret is advanced by the worm 60 until the work has been advanced nearly up to the grinding-wheels. At this time, determined by adjusting the shutter 8<u>, the tail of the pawl enters the gap and the pawl couples the worm-wheel 8<a> to the shaft 6<a>, the turret being then advanced at a slower speed. When the crank reaches the dead-centre, the tail of the pawl strikes the end of the gap and releases the worm-wheel 8<a>, the shaft 6<a> being then driven by the worm 60. The advance of the turret can be accelerated by pulling out a handle 8<z>, Fig. 5, secured to a weighted band 8<y> passing over a pulley 8<x> on the shaft 8<c>. This device is used mainly in dealing with thin blanks when the machine is adjusted to produce similar lenses from blanks of different thicknesses, since in this case the machine shutter 8<u> must be set for the thickest blank. At the end of the advance of the turret, the shaft 6<a> is arrested by a stop 9<c>, Fig. 5, and the turret is prevented from being withdrawn until the stop is relea ed by a hand-lever 9<e>, the operation of which reminds the attendant to substitute a fresh blank for the finished lens. The stop consists of a rod 9<c> which is formed at the end with a flat arranged, on rocking the rod, to move into or out of the path of a pin 9 on the collar 8<j>. The handle 9<e> has a lost-motion mounting, consisting of a key 9<f> engaging a slot in the rod, and the stop is operative or inoperative when the hand-lever is in the horizontal or the vertical position respectively. On lifting the handle, the turret can be withdrawn, and towards the end of the return stroke, a pin 2<d> on the slide 2 engages the handle and moves it into the horizontal position. The mechanism for rotating the turret comprises a coarse screw 10 on the shaft 1<b> engaging a nut 10<a>, Fig. 6, which is freely mounted in a collar 10<b>, the nut and the collar being prevented from moving laterally by a bracket 10<d>. The collar carries a pawl 10<g> engaging teeth 10<f> on the nut, and the collar is formed with a notch 10<i> which can engage a pawl 11 on a shaft 11<a>. The shaft 1<b> is provided with three equidistant stops 1<p>, 1<q>, 1<r> consisting of bars secured by nuts 1<t> in radial slots in a drum 1<h> which is secured to the shaft. To permit of slight angular adjustment, the drum may be secured by two thrust rods 1<i>, 1<j> which bear on faces 1<k>, 1 on the shaft and are engaged by adjusting-screws 1<m>, 1<n>. The stops 1<p>, 1<q>, 1<r> are arranged to engage a fixed stop 11<d> and to co-operate as described below with the bevelled end 11<c> of an arm 11<b> on the shaft 11<a> and with the bevelled end 11<e> of an arm 11<f> on a shaft 11<g>. The arms 11<b>, 11<e> are urged upwards by a spring 11<j>. During grinding, the turret is positioned by one of the stops 1<p>, 1<q>, 1<r> being held against the stop 11<d> by the arm 11<f>. When the turret is withdrawn, the rotation of the shaft 1<b> is prevented by the stops, and the shaft rotates the nut 10<a>. The collar 10<b> is rotated also, owing to the friction of the pawl, until the pawl 11 enters the recess 10i, the nut then rotating independently of the collar. Towards the end of the withdrawal of the turret the active stop 1<p>, 1<q>, or 1<r> rides off the stop 11<d> and the arm 11<b>, and the pawl 11 enters further into the notch 10i. During the advance of the turret, the nut is initially locked and the shaft 1<b> is compelled to rotate until the following stop 1<q> engages the stop 11<d> and depresses the arm 11<b>, thus releasing the pawl 11 and permitting the nut to rotate. A dash-pot 12 engaging the arm 11<f> is provided for cushioning the impact of the stops on the stop 11<d>. The grinding-wheels 4, 5 are arranged over a pan 7<d> and are provided with guards 4<v>, 5<m> and water-pipes, the pipe 50 for the wheel 5 supplying water to near the centre of the wheel. The wheel 5 is driven directly by an electromotor, as shown, by a belt 14 passing over a pulley on the shaft 5a and over pulleys 15 .. 18 mounted in the following manner to cause the belt to track properly when the slide-rest is adjusted or the table 5i is adjusted angularly. The pulleys 15,16 are carried by a link 21 pivoted